Bardarbunga volcano - New magma meeting Askja volcano in 2-4 days?

Bardarbunga volcano - New magma meeting Askja volcano in 2-4 days? HT: VolcanoDiscovery.


The intense seismic crisis caused by a significant laterally migrating magma intrusion continues to evolve with little changes. Earthquake activity has been a bit weaker yesterday, only to pick up again today. Two more magnitude 5+ quakes occurred after midnight near the caldera of the Bardarbunga central volcano.

The intrusion is now 45 km long and roughly 20 km deep, but so far remains mostly below 5 km depth. Horizontal spreading between the Dyngjuháls (DYNC) and Kverkfjöll (Gengissig, GSIG) GPS stations approaches 50 cm. At the moment, the expected most likely outcome scenario is a moderate to large fissure eruption, should the dyke eventually breach surface. The question is when this will occur, and where the magma exactly will be coming from:

What type of fissure eruption?

A question is whether it is fed by lateral magma movement from a reservoir beneath the Bardarbunga central volcano (typical flank eruption along a fissure) or in contact with the mantle source, so it could erupt as a rifting fissure eruption, and potentially become a very large event.

New magma meeting Askja volcano?

The front of the propagating fissure continued to move a bit north, towards the Asjka caldera. If the current propagation rate continues, it might hit this volcano in 2-4 days. In this scenario, it is feared that the new and hot intruding magma could start to interact with pockets of silica-rich (and hence very viscous, prone to explosive eruptions) older magma stored under Askja. The result could be potentially very explosive eruptions of the latter volcano, as two very different magmas interact and the equilibrium of the older magma chamber is disturbed: - the older silica-rich magma is heated up, can partially remelt and becomes less viscous, more able to flow. - the intruding, hot magma is cooled and dissolved gasses forced to form bubbles, causing overpressure of the system.

Inflation at Grimsvötn volcano

Interestingly, the neighboring large Grimsvötn volcano located to the southeast of Bárdarbunga seems to respond to the intrusion with a weak pulsating inflation pattern (GFUM station). There are no earthquakes under it suggesting that it is caused by an own intrusion.

Why this occurs is unclear. One interesting idea from VolcanCafe was "that the Bárðarbunga intrusion hit an old intrusion in Grimsvötns containing molten material and that it due to higher pressure in the Grimsvötn system took that infamous left-hand turn down Grimsvötns fissure swarm. It would certainly explain the marked pulsing on the GPS plot."

The earthquake this morning at the north/northwestern part of the caldera at 6 km depth at 01:26 UTC could have been the biggest in the current swarm. Estimated magnitudes range from 4.1 (IMO) to 5.7 (USGS).

The magma intrusion (dyke) north of Dyngjujokull is still migrating and stretches now approx. 10 km outside of the glacier. It will be interesting to see what happens when it reaches the area of the Asjka fissure swarm. A possibility could be that older dykes from that one stop the propagation of the Bardarbunga intrusion, another that it activates Askja as well.